▎ 摘　　要

We report on a demonstration of top-gated graphene field-effect transistors (FETs) fabricated on epitaxial SiC substrate. Composite stacks, benzocyclobutene and atomic layer deposition Al2O3, are used as the gate dielectrics to maintain intrinsic carrier mobility of graphene. All graphene FETs exhibit n-type transistor characteristics and the drain current is nearly linear dependence on gate and drain voltages. Despite a low field-effect mobility of 40 cm(2)/(V s), a maximum cutoff frequency of 4.6 GHz and a maximum oscillation frequency of 1.5 GHz were obtained for the graphene devices with a gate length of 1 mu m.